Perforated pipe cutting method and device based on machine vision

Abstract

The invention discloses a perforated pipe cutting method and device based on machine vision. The device comprises a flying saw, a speed measuring mechanism, an encoder and a machine vision device. The machine vision device is matched with the encoder of the speed measuring mechanism, the flying saw is combined to complete fixed-length cutting of the tubular product with the hole shape, and the positioning precision of the hole shape can be smaller than or equal to 0.2 mm. According to the characteristics of machine vision, when a high-resolution camera is selected to be matched with a lens of a corresponding visual field, the measurement precision can reach 0.01 mm, and the method is not like that a laser sensor is positioned by a light spot, and the photographing mode of the machine vision device is not influenced by material vibration; when the hole shape of the material is changed, only software setting needs to be changed, direct production can be achieved without adjusting hardware, and the production efficiency is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of welded pipe cutting, and relates to a pipe cutting method, and in particular to a method and device for cutting a perforated pipe based on machine vision. Background Art

[0002] The demand for perforated pipes in the current market is constantly expanding. The process of producing such pipes is to first punch out the required hole shape on the strip, then roll it into shape and weld it through a forming unit, and finally cut the continuously produced pipes into the required fixed length online by a flying saw.

[0003] This type of perforated pipe often has strict requirements on the distance accuracy of various hole shapes relative to the pipe end while controlling the cut-to-length. If the tolerance is exceeded, it will be scrapped, so higher requirements are placed on the cut-to-length accuracy of the flying saw.

[0004] The previous solution was to use a laser sensor (which emits laser light directly at the center of the hole to measure the position of the hole) in conjunction with an encoder of a speed measuring mechanism (which is used to measure the length of the material) to solve the problems of sizing and hole position accuracy.

[0005] But the disadvantages of this solution are: (1) Due to the limitation of the positioning accuracy of the laser sensor (0.5 mm), it cannot meet the higher positioning accuracy requirements of fixed length; (2) Moreover, when the material vibrates, it is difficult for the laser sensor to ensure accurate measurement of small circular holes (the laser sensor needs to emit laser light directly at the center of the hole); (3) Furthermore, when the material type or hole shape changes, the laser sensor needs to change and adjust its position, which brings inconvenience to production. Summary of the invention

[0006] In view of the shortcomings and deficiencies in the prior art, the object of the present invention is to provide a method and device for cutting perforated pipes based on machine vision.

[0007] The technical solution of the present invention is as follows: A method for cutting a perforated tube based on machine vision, the method comprising: The real-time length L and speed of the perforated pipe passing through the flying saw are measured by the speed measuring mechanism and the encoder; At the same time, the machine vision device continuously takes pictures to obtain the distance L2 from the fixed measurement mark block to the hole shape, and the distance L1 from the measurement mark block to the origin of the flying saw is known; Then, L1 and L2 are used to accurately calibrate the current hole position. When the length and hole position meet the set requirements, the control system starts the flying saw and cuts the hole-shaped pipe synchronously.

[0008] Furthermore, the requirement is: while giving priority to ensuring that the distance between the cut-off point, i.e., the pipe end and the hole edge meets the dimensional tolerance requirement, ensuring that the real-time length L of the pipe is also within the tolerance range of the set fixed length L0.

[0009] Furthermore, L1 - L2 is the distance from the edge of the hole to the origin of the flying saw, which is used to determine the precise position of the cut-off point and the edge of the hole, thereby ensuring the dimensional tolerance.

[0010] Furthermore, the perforated pipe is in contact with the surface of the speed measuring roller of the speed measuring mechanism in the forward direction of the pipe movement, thereby driving the speed measuring roller to roll. The encoder is coaxially connected to the speed measuring roller. The circumference of the speed measuring roller is equivalent to the number of pulses of one circle of the encoder. By accumulating the pulses of the encoder, the real-time length L of the current perforated pipe passing through the flying saw can be obtained.

[0011] A perforated pipe cutting device based on machine vision, the device comprising a control system, a flying saw, a speed measuring mechanism, an encoder, a measuring marking block and a machine vision device, wherein the control system is respectively connected to the flying saw, the speed measuring mechanism, the encoder and the machine vision device for communication; The speed measuring mechanism and the encoder are connected to each other to measure the real-time length L of the perforated pipe; The machine vision device is used to continuously take pictures of the hole shapes of the perforated pipes; The measuring mark block is fixedly arranged on the side surface of the perforated pipe.

[0012] Furthermore, the machine vision device includes an industrial camera installed above the perforated pipe, a light source, and an industrial computer and a light source controller electrically connected thereto.

[0013] Furthermore, the machine vision device is arranged at the entrance side of the flying saw car and is located on the right side of the speed measuring mechanism and the encoder.

[0014] Furthermore, the device also includes a forming unit, which is located on the left side of the speed measuring mechanism and the encoder and is used to roll and form the perforated steel strip and weld it into a perforated pipe.

[0015] Furthermore, the device also includes a bracket for supporting the cut perforated pipe.

[0016] The beneficial effects of the present invention are as follows: (1) The present invention uses a machine vision device in conjunction with an encoder of a speed measuring mechanism, combined with a flying saw to complete the cut-to-length cutting of a perforated pipe. Combined with the mechanical and control accuracy, the positioning accuracy of the hole shape can reach less than or equal to 0.2 mm.

[0017] (2) Based on the characteristics of machine vision, the present invention can easily achieve a measurement accuracy of 0.01 mm when a high-resolution camera is used in conjunction with a lens with a corresponding field of view. Moreover, unlike laser sensors that rely on light spot positioning, the way machine vision devices take pictures will not be affected by material vibration. (3) By utilizing the present invention, when the hole shape of the material changes, only the software settings need to be changed (for example, the calibration of the edge position when the hole shape is circular, square or special-shaped, etc.), and production can be directly carried out without adjusting the hardware, thereby greatly improving production efficiency.

[0018] (4) The present invention has a compact structure and can continuously cut perforated pipes to a fixed length, with good cutting effect, high product quality and easy operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of a method for cutting a perforated pipe based on machine vision according to the present invention; Among them, 1 is a flying saw bed, 2 is a flying saw car, 3 is a machine vision device, 4 is a speed measuring mechanism, 5 is a forming unit, 6 is a perforated pipe, 7 is an encoder, and 8 is a measuring mark block. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0021] like Figure 1 As shown, the perforated pipe cutting device based on machine vision of this embodiment includes a control system, a flying saw, a speed measuring mechanism 4, an encoder 7 and a machine vision device 3, and the control system is respectively connected to the flying saw, the speed measuring mechanism 4, the encoder 7 and the machine vision device 3 for communication; The speed measuring mechanism 4 and the encoder 7 are arranged on the right side of the forming unit 5 for the perforated pipe 6, and the speed measuring mechanism 4 and the encoder 7 are connected to each other.

[0022] The speed measuring mechanism 4 includes a speed measuring roller, which is used to measure the real-time length L of the perforated pipe 6. Specifically, the perforated pipe 6 and the surface of the speed measuring roller of the speed measuring mechanism 4 are in forward contact along the moving direction of the pipe, thereby driving the speed measuring roller to roll, and the encoder 7 is coaxially connected to the speed measuring roller, so that the circumference of the speed measuring roller is equivalent to the number of pulses of the encoder 7 in one circle, and the control system can calculate the current length and speed of the perforated pipe 6 passing through the flying saw by accumulating the pulses of the encoder 7.

[0023] The machine vision device 3 is arranged at the entrance side of the flying saw 2 and is located on the right side of the speed measuring mechanism 4 and the encoder 7, and is used to take pictures of the hole shape of the hole-shaped pipe 6.

[0024] The machine vision device 3 includes an industrial camera and corresponding lenses, light sources, industrial computers, etc.; The machine vision device 3 of this embodiment adopts existing technology, such as purchased from manufacturers such as Cognex and Hikvision.

[0025] Among them, the flying saw machine is used to cut the porous pipe 6, including a flying saw bed 1 and a flying saw car 2 arranged on the flying saw bed 1. The control system controls the flying saw car 2 to move back and forth on the flying saw bed 1, and the speed of the flying saw car 2 is adjustable to synchronize the speed and position of the porous pipe 6.

[0026] like Figure 1 As shown, the perforated pipe cutting device based on machine vision in this embodiment also includes a forming unit 5, which is located on the left side of the speed measuring mechanism 4 and the encoder 7, and is used to roll the perforated steel strip into shape and weld it into a perforated pipe 6.

[0027] The perforated pipe cutting device based on machine vision in this embodiment further includes a bracket ( Figure 1 not shown on the right).

[0028] The measurement marking block 8 is an artificially set marking block used to measure the relative distance.

[0029] The working principle of cutting using the perforated pipe cutting device based on machine vision of this embodiment is as follows: The distance L1 from the measuring mark block 8 to the origin of the flying saw 2 is known. The distance L2 from the measuring mark block 8 to the hole is measured by the machine vision device 3. The real-time length L of the pipe is measured by the encoder 7 of the speed measuring mechanism 4. The real-time length L of the pipe is compared with the set length L0 (with hole position tolerance requirements). The flying saw 2 is started in time to synchronize the speed and position of the material (hole-shaped pipe 6), and the hole-shaped pipe 6 with a fixed length of L0 is cut.

[0030] Since L1 can be accurately measured, L2 is measured accurately by the machine vision device 3 to meet the distance accuracy requirement of the hole relative to the pipe end. Combined with the encoder 7 of the speed measuring mechanism 4, the control system can obtain the precise position of the hole relative to the flying saw 2 in real time, thereby being able to accurately control the length of the material to be cut and meet the sizing requirement of the hole-shaped pipe 6.

[0031] The working process of cutting using the perforated pipe cutting device based on machine vision of this embodiment is as follows: The perforated steel strip is continuously formed and high-frequency welded by the forming unit 5 to form a perforated tube 6, which then passes through the speed measuring mechanism 4 and the machine vision device 3 and enters the flying saw process to be cut according to the set requirements.

[0032] The perforated pipe 6 contacts the surface of the speed measuring roller of the speed measuring mechanism 4 in the forward direction of the pipe movement, thereby driving the speed measuring roller to roll. The encoder 7 is coaxially connected to the speed measuring roller, so that the circumference of the speed measuring roller is equivalent to the number of pulses of one circle of the encoder 7. The control system can calculate the current length of the perforated pipe 6 passing through the flying saw by accumulating the pulses of the encoder 7.

[0033] The machine vision device 3 includes an industrial camera installed above the perforated pipe 6, a light source, an industrial computer and a light source controller electrically connected thereto. Figure 1 The figure 3 is a schematic diagram of the situation after the industrial camera takes the photo, wherein the figure 8 is a measuring mark block 8 installed on the side of the hole-shaped pipe 6 (the distance between its edge and the origin of the flying saw is L1), which is used to measure the relative distance L2 between the hole shape and the measuring mark block 8 in the photo, and the calculation of L1 - L2 is the distance from the edge of the hole shape to the origin of the flying saw 2.

[0034] The industrial camera takes continuous high-speed photos under the control of the industrial computer. When a hole shape appears in the photograph, the precise relative position L2 of the hole shape can be measured.

[0035] The control system calculates the length and speed of the hole-shaped pipe 6 in real time according to the accumulation of the encoder 7, and then accurately corrects the current hole position through L1 and L2. When the accumulated length and the hole position meet the set requirements, the control system starts the flying saw 2 to synchronize and cut the hole-shaped pipe 6. The cutting position and the hole edge meet the set requirements. The flying saw 2 returns to the origin after completing the cutting.

[0036] The above embodiments are only for illustrating the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for cutting perforated pipes based on machine vision, characterized in that: The method comprises: The real-time length L and speed of the perforated pipe passing through the flying saw are measured by the speed measuring mechanism and the encoder; At the same time, the machine vision device continuously takes pictures to obtain the distance L2 from the fixed measurement mark block to the hole shape, and the distance L1 from the measurement mark block to the origin of the flying saw is known; Then, L1 and L2 are used to accurately calibrate the current hole position. When the length and hole position meet the set requirements, the control system starts the flying saw and cuts the hole-shaped pipe synchronously.

2. A method for cutting a perforated pipe based on machine vision as claimed in claim 1, characterized in that: The requirement is: to give priority to ensuring that the distance between the cut-off point, i.e., the pipe end and the hole edge, meets the dimensional tolerance requirement, while ensuring that the real-time length L of the pipe is also within the tolerance range of the set fixed length L0.

3. A method for cutting a perforated pipe based on machine vision as claimed in claim 1 or 2, characterized in that: L1-L2 is the distance from the edge of the hole to the origin of the flying saw, which is used to determine the precise position of the cut-off point and the edge of the hole, thereby ensuring the dimensional tolerance.

4. A method for cutting a perforated pipe based on machine vision as claimed in claim 1 or 2, characterized in that: The perforated pipe is in contact with the surface of the speed measuring roller of the speed measuring mechanism in the forward direction of the pipe movement, thereby driving the speed measuring roller to roll. The encoder is coaxially connected to the speed measuring roller. The circumference of the speed measuring roller is equivalent to the number of pulses of one circle of the encoder. The real-time length L of the current perforated pipe passing through the flying saw can be obtained by accumulating the pulses of the encoder.

5. A perforated pipe cutting device based on machine vision, characterized in that: The device comprises a control system, a flying saw machine, a speed measuring mechanism, an encoder, a measuring marking block and a machine vision device, wherein the control system is respectively connected to the flying saw machine, the speed measuring mechanism, the encoder and the machine vision device for communication; The speed measuring mechanism and the encoder are connected to each other to measure the real-time length L of the perforated pipe; The machine vision device is used to continuously take pictures of the hole shapes of the perforated pipes; The measuring mark block is fixedly arranged on the side surface of the perforated pipe.

6. The device according to claim 5, characterized in that The machine vision device comprises an industrial camera installed above the perforated pipe, a light source, and an industrial computer and a light source controller electrically connected thereto.

7. The device according to claim 5 or 6, characterized in that The machine vision device is arranged at the entrance side of the flying saw car and is located on the right side of the speed measuring mechanism and the encoder.

8. The device according to claim 5 or 6, characterized in that The device also includes a forming unit, which is located on the left side of the speed measuring mechanism and the encoder and is used for rolling and welding the perforated steel strip into a perforated pipe.

9. The device according to claim 5 or 6, characterized in that The device also includes a bracket for holding the cut perforated pipe.

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